Sunday, August 7, 2011

Doonesbury Whiffs on White Roofs

Today's edition of Doonesbury uses white roofs as part of the joke, and while I'm excited for the concept to reach a new audience ... the comic gets their economic benefits wrong, severely underestimating their impact.

If white roofs didn't deliver year-round energy savings, why would anyone do it? Yet that's exactly what Garry Trudeau's character Mike Doonesbury mistakenly claims.

As Mother Jones' Kiera Butler detailed last year, white roofs are a net energy win no matter where you live:
The latest white-roofs study used computer simulations to figure out what might happen if every roof in every city of the world were white. The finding: An average temperature reduction of .7 degrees Fahrenheit. Good news in general, but here’s the problem for homeowners: Since white roofs cool buildings all year round, some people have pointed out that folks with white roofs in northern climates might end up cranking the thermostat higher than their neighbors with dark-colored roofs during winter months.

Roofs of the future might solve this problem: Last year, a team of MIT researchers came up with a prototype of high-tech tiles that change color based on the air temperature. A cool idea for sure, but unfortunately the smart tiles aren't on the market yet. So till they are, should you spring for a white roof even if you live in the chilly north? Hashem Akbari, a senior scientist and leader of the Heat Island Group at the Lawrence Berkeley National Laboratory, says yes, since AC typically uses a lot more energy than heat. "The wintertime penalties are only a fraction of summer time savings."
White roofs can save up to 20% of a building's energy costs on a hot day, as Bill Clinton recently wrote in Newsweek. The further south you go, the more in energy savings you'll see from having one - but even in Maine, you'll see a net benefit. Makes sense - not only does AC cost more than heat, but deflecting strong summer sun is a bigger benefit than absorbing much weaker winter sun.

And above & beyond the net energy benefit, white roofs would cut the urban heat island effect and take some of the edge off global warming. So why aren't we putting people to work painting every roof white?
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